The Flying Doctor: Mosquito magnets

Doctor Peter Barrett looks at the ins and outs of insect attraction

12:00AM GMT 20 Feb 1999

ARE some people more attractive than others? Mosquitoes would appear to think so.

If you have ever been on holiday and found yourself eaten alive while your travelling companion has escaped without a bite, you will find comfort in some new scientific research. Controlled laboratory trials have shown that some people do seem to be bitten more frequently than others.

Mosquitoes are clearly attracted to carbon dioxide (which we all breathe out) and it is likely that they follow a concentration gradient to home in on their victims. As they get closer, body heat also appears to act as an attractant.

But there are many other chemicals present on the skin which tempt mosquitoes and it is variations in the concentrations of these which may explain the difference in individual bite rates.

In an experiment in Holland, researchers asked a group of volunteers to sit, wearing only their underwear, in a room full of hungry mosquitoes. They found that they tended to be bitten around the ankles and feet. After washing their feet with unperfumed antiseptic soap, the bites were found to be far more randomly distributed.

It transpires that there are bacteria, which thrive in the crevices between the toes. These bacteria produce a chemical responsible for the smell of smelly feet. A relative of this bacterium is used in the production of limburger cheese, and when the researchers baited mosquito traps with ripe limburger they found that they trapped many more mosquitoes.

More recently, I saw a report that claimed to show that mosquitoes were attracted to human sex pheromones.

So, taking the above into account, you can reduce the chances of being bitten by holding your breath, immersing yourself in ice cold water, ensuring that your feet are clean and avoiding limburger sandwiches. You should also make sure that you travel only with those you find physically repulsive. Alternatively, carry an effective insect repellent.

For advice on immunisations and the latest health news you can obtain a written health brief by telephoning the Travellers' Health Line on 09068 224100.